The impact will be monitored before this option is removed from all train stations next year.

Cash top-up options will then be removed from the General Ticketing Machines (GTMs) at stations, while cashless top-up options will be expanded.

Since January, the option of topping up stored-value cards using bank cards and mobile payment platforms such as Apple Pay and Android Pay have been available at all GTMs.

Mr Lam Wee Shann, LTA's group director for technology and industry development, said the Thomson-East Coast Line, due to open in 2019, will be the first cashless rail line.

"With more than 7 million ticketing transactions each day, a fully cashless public transport system will be an important step in Singapore's quest to become a cashless society and a Smart Nation," he said.

He said cashless payments will also be extended to private transport and parking, with details to be shared "when ready".

LTA data shows that about 27 per cent of commuters still pay cash at MRT passenger service centres to top up their travel cards. Top-ups with cash can still be done at convenience stores in 2020.

Buses will only accept travel cards by 2020. Less than 2 per cent of bus journeys are paid for in cash. LTA is "still studying" what to do if a commuter boards without a travel card.

Mr Ang Hin Kee, deputy chairman for the Government Parliamentary Committee for Transport, said there are concerns about the elderly adapting to a cashless system, but he remains optimistic.

"We need not see it as a case of them never learning to use it but should instead find a way to help them bridge the gap," he told The New Paper.

"The onus will be on operators to make the system auntie-friendly."

Singapore University of Social Sciences lecturer Park Byung Joon, who specialises in urban transport, was also concerned about tourists.

"A lot of tourists use public transport when they visit Singapore. It may be quite cumbersome if they have to set up an account just to use public transport," he said.

To tackle these issues, LTA and TransitLink said service agents will assist commuters at stations, and information will be available at ticketing touchpoints and on media platforms.

They will also work with other agencies and grassroots organisations to assist commuters to acquire banking facilities where necessary.